docs: def addUniqueValue(self, value, label, description, symbol):
          """
          adds a unique value to the renderer
          """
          if self._uniqueValueInfos is None:
              self._uniqueValueInfos = []
          self._uniqueValueInfos.append(
              {
                  "value" : value,
                  "label" : label,
                  "description" : description,
                  "symbol" : symbol
              }
          )